1. Field of the Invention
The invention relates to the general field of bearings, linear and rotary, and in particular such bearings for use as bushings for tandem axle vehicle suspension systems among other machines.
2. Description of the Prior Art
The bearing of the invention being particularly useful in connection with center bushings in tandem axle vehicle suspension systems, the bearing of the invention will be discussed primarily in connection with such use. The bearing of the invention is an improvement upon the structure disclosed in U.S. Pat. No. 3,458,214 granted Jul. 29, 1969 to the inventor herein, said '214 patent being incorporated by reference herein. The context of the present invention is described in detail in the '214 patent and thus will be discussed briefly herein.
Tandem axle suspension systems for rear vehicle wheels are widely used in connection with large load-bearing capacity vehicles such as tractor and trailers, trucks, and the like. Tandem axle suspension systems include as a key element thereof bearing assemblies mounted in equalizer beams which are part of the tandem axle suspension systems in connection with axles of the vehicles. The beams are mounted pivotally by their ends to the axles and by their mid-points to brackets attached to the vehicle chassis. The bearings of the invention and of the '214 patent are useable in connection with such bearing assemblies on equalizer beams including beam center bushings and beam end bushings.
The structure in the '214 patent successfully addressed a number of the needs and deficiencies of prior bearing assemblies including the deficiencies inherent in rubber center bushings, awkward and inconvenient replacement of such bushings, deterioration of rubber bushings and inadequate lubrication of non-elastomer bushings. In addition, the '214 patent successfully addressed the then existing need for more conveniently installed bearings.
The progress of commerce and in particular the demands of ever-greater efficiency and safety in all sectors of the economy including transportation, have rendered it desirable to improve the structure and installation of, as well as tools used in connection with fabricating bearing assemblies, particularly in heavy weight-bearing capacity vehicles such as trucks. Materials, such as aluminum, of parts used in conjunction with bushings, may be attacked and weakened by harsh chemicals, causing breakage and resulting potential for serious accidents. In addition,a common problem arises when existing seals rub on the shaft or internal bearing member, causing grooves to be worn creating a stress riser tending to cause the shaft to break, with resulting potential for accidents. There has been a felt but unfulfilled need for efficiently-sealed and readily installable and conveniently lubricated bushings.
Under existing methods, machining of parts for bushings is performed to a given diameter, and bushings with thin walls may be difficult to bore accurately due to their flexible nature and their frequently non-uniform wall thickness and out-of-round condition. Therefore, there has been a felt but unfullfilled need for methods and apparatus for machining tubing to specific wall thicknesses and to selected size of internal bore.